Construction of Hierarchical NiCoSeCoS Core–Shell Nanotube Arrays for High-Performance Hybrid Supercapacitor

In this work, core–shell NiCoSe@CoS nanotube arrays directly grown on nickel foam were synthesized via a two-step hydrothermal method combined with cyclic voltammetry electrodeposition. In such heterostructures, NiCoSe nanotubes as the core are wrapped by interconnected CoS nanosheets as the shell. Results showed that the obtained NiCoSe@CoS nanotube arrays form a conductive 3D network by growing CoS nanosheets on the surface of the NiCoSe nanotubes, which increase electroactive sites, shorten ion diffusion pathways, and thus enhance charge storage. The unique core–shell heterostructures improved the structural stability and accelerated the electrode reaction kinetics of the nanotube arrays. Compared with the single-phase CoS nanosheets and NiCoSe nanotube arrays, the NiCoSe@CoS nanotube arrays as electrodes demonstrated enhanced areal capacitance (3.28 and 2.22 F cm−2 at 3 and 30 mA cm−2, respectively) and cyclic stability (capacity retention rate of 93% after 5000 cycles at 3 mA cm−2). Furthermore, the NiCoSe@CoS nanotube arrays were used as the positive electrode to assemble hybrid supercapacitor devices with carbon nanotubes as the negative electrode. The obtained device can deliver an energy density of 36.3 Wh kg−1 at a power density of 801.7 W kg−1 with a long-term cycling stability, which indicates that the NiCoSe@CoS nanotube arrays have a greatly practical application value in supercapacitor devices